Flexible vascular occluding device

ABSTRACT

A vascular occluding device for modifying blood flow in a vessel, while maintaining blood flow to the surrounding tissue. The occluding device includes a flexible, easily compressible and bendable occluding device that is particularly suited for treating aneurysms in the brain. The neurovascular occluding device can be deployed using a micro-catheter. The occluding device can be formed by braiding wires in a helical fashion and can have varying lattice densities along the length of the occluding device. The occluding device could also have different lattice densities for surfaces on the same radial plane.

RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.15/847,384, filed Dec. 19, 2017, which is a continuation of U.S. patentapplication Ser. No. 14/791,876, filed Jul. 6, 2015, now issued as U.S.Pat. No. 9,855,047, which is a continuation of U.S. patent applicationSer. No. 13/845,162, filed Mar. 18, 2013, now issued as U.S. Pat. No.9,125,659, which is a continuation of U.S. patent application Ser. No.11/136,395, filed on May 25, 2005, now issued as U.S. Pat. No.8,398,701, which claims priority benefit of U.S. Provisional ApplicationNo. 60/574,429, filed on May 25, 2004. Each of the aforementionedapplications is incorporated by reference in its entirety herein.

FIELD OF THE INVENTION

The invention relates generally to an implantable device that could beused in the vasculature to treat common vascular malformations. Moreparticularly, it relates to a flexible, biocompatible device that can beintroduced into the vasculature of a patient to embolize and occludeaneurysms, particularly cerebral aneurysms.

BACKGROUND OF THE INVENTION

Walls of the vasculature, particularly arterial walls, may developpathological dilatation called an aneurysm. Aneurysms are commonlyobserved as a ballooning-out of the wall of an artery. This is a resultof the vessel wall being weakened by disease, injury or a congenitalabnormality. Aneurysms have thin, weak walls and have a tendency torupture and are often caused or made worse by high blood pressure.Aneurysms could be found in different parts of the body; the most commonbeing abdominal aortic aneurysms (AAA) and the brain or cerebralaneurysms. The mere presence of an aneurysm is not alwayslife-threatening, but they can have serious heath consequences such as astroke if one should rupture in the brain. Additionally, as is known, aruptured aneurysm can also result in death.

The most common type of cerebral aneurysm is called a saccular aneurysm,which is commonly found at the bifurcation of a vessel. The locus ofbifurcation, the bottom of the V in the Y, could be weakened byhemodynamic forces of the blood flow. On a histological level, aneurysmsare caused by damage to cells in the arterial wall. Damage is believedto be caused by shear stresses due to blood flow. Shear stress generatesheat that breaks down the cells. Such hemodynamic stresses at the vesselwall, possibly in conjunction with intrinsic abnormalities of the vesselwall, have been considered to be the underlying cause for the origin,growth and rupture of these saccular aneurysms of the cerebral arteries(Lieber and Gounis, The Physics of Endoluminal stenting in the Treatmentof Cerebrovascular Aneurysms, Neurol Res 2002: 24: S32-S42). Inhistological studies, damaged intimal cells are elongated compared toround healthy cells. Shear stress can vary greatly at different phasesof the cardiac cycle, locations in the arterial wall and among differentindividuals as a function of geometry of the artery and the viscosity,density and velocity of the blood. Once an aneurysm is formed,fluctuations in blood flow within the aneurysm are of criticalimportance because they can induce vibrations of the aneurysm wall thatcontribute to progression and eventual rupture. For a more detaileddescription of the above concepts see, for example, Steiger,Pathophysiology of Development and Rupture of Cerebral Aneurysms, ActaNeurochir Suppl 1990: 48: 1-57; Fergueson, Physical Factors in theInitiation, Growth and Rupture of Human Intracranial Saccular Aneurysms,J Neurosurg 1972: 37: 666-677.

Aneurysms are generally treated by excluding the weakened part of thevessel from the arterial circulation. For treating a cerebral aneurysm,such reinforcement is done in many ways: (i) surgical clipping, where ametal clip is secured around the base of the aneurysm; (ii) packing theaneurysm with microcoils, which are small, flexible wire coils; (iii)using embolic materials to “fill” an aneurysm; (iv) using detachableballoons or coils to occlude the parent vessel that supplies theaneurysm; and (v) endovascular stenting. For a general discussion andreview of these different methods see Qureshi, Endovascular Treatment ofCerebrovascular Diseases and Intracranial Neoplasms, Lancet. 2004 Mar.6; 363 (9411):804-13; Brilstra et al. Treatment of IntracranialAneurysms by Embolization with Coils: A Systematic Review, Stroke 1999;30: 470-476.

As minimally invasive interventional techniques gain more prominence,microcatheter based approaches for treating neurovascular aneurysms arebecoming more prevalent. Micro-catheters, whether flow-directed orwire-directed, are used for dispensing embolic materials, microcoils orother structures (e.g., stents) for embolization of the aneurysm. Amicrocoil can be passed through a microcatheter and deployed in ananeurysm using mechanical or chemical detachment mechanisms, or bedeployed into the parent vessel to permanently occlude it and thus blockflow into the aneurysm. Alternatively, a stent could be tracked throughthe neurovasculature to the desired location. Article by Pereira,History of Endovascular Aneurysms Occlusion in Management of CerebralAneurysms; Eds: Le Roux et al., 2004, pp: 11-26 provides an excellentbackground on the history of aneurysm detection and treatmentalternatives.

As noted in many of the articles mentioned above, and based on theorigin, formation and rupture of the cerebral aneurysm, it is obviousthat the goal of aneurysmal therapy is to reduce the risk of rupture ofthe aneurysm and thus the consequences of sub-arachnoid hemorrhage. Itshould also be noted that while preventing blood from flowing into theaneurysm is highly desirable, so that the weakened wall of the aneurysmdoesn't rupture, it may also be vital that blood flow to the surroundingstructures is not limited by the method used to obstruct blood flow tothe aneurysm. Conventional stents developed for treating other vascularabnormalities in the body are ill suited for embolizing cerebralaneurysms. This could lead to all the usual complications when highoxygen consumers, such as brain tissue, are deprived of the needed bloodflow.

There are many shortcomings with the existing approaches for treatingneurovascular aneurysms. The vessels of the neurovasculature are themost tortuous in the body; certainly more tortuous than the vessels ofthe coronary circulation. Hence, it is a challenge for the surgeon tonavigate the neurovasculature using stiff coronary stents that aresometimes used in the neurovasculature for treating aneurysms. Thebending force of a prosthesis indicates the maneuverability of theprosthesis through the vasculature; a lower bending force would implythat the prosthesis is more easily navigated through the vasculaturecompared to one with a higher bending force. Bending force for a typicalcoronary stent is 0.05 lb-in (force to bend 0.5 inches cantilever to 90degree). Hence, it will be useful to have neural prosthesis that is moreflexible than existing stents.

Existing stent structures, whether used in coronary vessels or in theneurovasculature (microcoils) are usually straight, often laser cut froma straight tubing or braiding with stiff metallic materials. However,most of the blood vessels are curved. Hence, current stent structuresand microcoils impart significant stress on the vessel walls as they tryto straighten a curved vessel wall. For a weakened vessel wall,particularly where there is a propensity for an aneurysm formation, thiscould have disastrous consequences.

As noted earlier, the hemodynamic stress placed on the blood vessels,particularly at the point of bifurcation, leads to weakening of thevessel walls. The most significant source of such stress is the suddenchange in direction of the blood flow. Hence, if one were to minimizethe sudden change in direction of blood flow, particularly at thelocation of vessel weakness, it would be beneficial.

Existing approaches to occluding aneurysms could lead to another set ofproblems. Methods that merely occlude the aneurysm by packing or fillingit with embolic material (coils or liquid polymers) do not address thefundamental flow abnormalities that contribute to the formation ofaneurysm.

Currently, many different stent structures and stent deployment methodsexist. A stent structure could be expanded after being placedintraluminally on a balloon catheter. Alternatively, self-expandingstents could be inserted in a compressed state and expanded upondeployment. All the stents need to have the radial rigidity to maintainpatency of the lumen and simultaneously have the longitudinalflexibility to facilitate navigating the tortuous path of thevasculature. For balloon expandable stents, the stent is mounted on aballoon at the distal end of a catheter, the catheter is advanced to thedesired location and the balloon is inflated to expand the stent into apermanent expanded condition. The balloon is then deflated and thecatheter withdrawn leaving the expanded stent to maintain vesselpatency. Because of the potentially lethal consequences of dissecting orrupturing an intracerebral vessel, the use of balloon expandable stentsin the brain is fraught with problems. Proper deployment of a balloonexpandable stent requires slight over expanding of the balloon mountedstent to embed the stent in the vessel wall and the margin of error issmall. Balloon expandable stents are also poorly suited to adapt to thenatural tapering of cerebral vessels which taper proximally to distally.If a stent is placed from a parent vessel into a smaller branch vesselthe change in diameter between the vessels makes it difficult to safelydeploy a balloon expandable stent. A self-expanding stent, where thecompressed or collapsed stent is held by an outer restraining sheathover the compressed stent to maintain the compressed state untildeployment. At the time of deployment, the restraining outer sheath isretracted to uncover the compressed stent, which then expands to keepthe vessel open. Additionally, the catheters employed for deliveringsuch prosthesis are micro-catheters with outer diameter of 0.65 mm to1.3 mm compared to the larger catheters that are used for delivering thelarge coronary stents to the coronaries.

Various stent structures and solutions have been suggested for treatingcerebral aneurysms. U.S. Pat. No. 6,669,719 (Wallace et al.) describes astent and a stent catheter for intra-cranial use. A rolled sheet stentis releasably mounted on the distal tip of a catheter. Upon the rolledsheet being positioned at the aneurysm, the stent is released. Thisresults in immediate and complete isolation of an aneurysm andsurrounding side branches of the circulatory system and redirectingblood flow away from the aneurysm. A significant drawback of such asystem is that the surrounding side branches, along with the targetaneurysm, are deprived of the needed blood flow after the stent has beendeployed.

U.S. Pat. No. 6,605,110 (Harrison) describes a self-expanding stent fordelivery through a tortuous anatomy or for conforming the stent to acurved vessel. This patent describes a stent structure with radiallyexpandable cylindrical elements arranged in parallel to each other andinterspersed between these elements and connecting two adjacentcylindrical elements are struts that are bendable. While this structurecould provide the necessary flexibility and bendability of the stent forcertain applications, it is expensive and complex to manufacture.

U.S. Pat. No. 6,572,646 (Boylan) discloses a stent made up of asuper-elastic alloy, such as Ni—Ti alloy (Nitinol), with a lowtemperature phase that induces a first shape to the stent and a hightemperature phase that induces a second shape to the stent with a bendalong the length. U.S. Pat. No. 6,689,162 (Thompson) discloses a braidedprosthesis that uses strands of metal, for providing strength, andcompliant textile strands. The objective of Thompson is to have aprosthesis that combines the structural strength and resiliency of aself-expanding stent and the low permeability of a graft. U.S. Pat. No.6,656,218 (Denardo et al.) describes an intravascular flow modifier thatallows microcoil introduction even after placing the modifier.

SUMMARY OF THE INVENTION

An aspect of the present invention provides a highly flexibleimplantable occluding device that can easily navigate the tortuousvessels of the neurovasculature. Additionally, occluding device caneasily conform to the shape of the tortuous vessels of the vasculature.Furthermore, the occluding device can direct the blood flow within avessel away from an aneurysm; additionally such an occluding deviceallows adequate blood flow to be provided to adjacent structures suchthat those structures, whether they are branch vessels or oxygendemanding tissues, are not deprived of the necessary blood flow.

The occluding device is also capable of altering blood flow to theaneurysm, yet maintaining the desired blood flow to the surroundingtissue and within the vessel. In this instance, some blood is stillallowed to reach the aneurysm, but not enough to create a laminar flowwithin the aneurysm that would cause injury to its thinned walls.Instead, the flow would be intermittent, thereby providing sufficienttime for blood clotting or filler material curing within the aneurysm.

The occluding device is flexible enough to closely approximate thenative vasculature and conform to the natural tortuous path of thenative blood vessels. One of the significant attributes of the occludingdevice according to the present invention is its ability to flex andbend, thereby assuming the shape of a vasculature within the brain.These characteristics are for a neurovascular occluding device thancompared to a coronary stent, as the vasculature in the brain is smallerand more tortuous.

In general terms, aspects of the present invention relate to methods anddevices for treating aneurysms. In particular, a method of treating ananeurysm with a neck comprises deploying a vascular occluding device inthe lumen of a vessel at the location of the aneurysm, whereby the bloodflow is redirected away from the neck of the aneurysm. The inducedstagnation of the blood in the lumen of the aneurysm would createembolization in the aneurysm. The occluding device spans the width ofthe stem of the aneurysm such that it obstructs or minimizes the bloodflow to the aneurysm. The occluding device is very flexible in both itsmaterial and its arrangement. As a result, the occluding device can beeasily navigated through the tortuous blood vessels, particularly thosein the brain. Because the occluding device is flexible, very littleforce is required to deflect the occluding device to navigate throughthe vessels of the neurovasculature, which is of significance to theoperating surgeon.

A significant feature of the occluding device, apart from itsflexibility, is that the occluding device may have an asymmetrical braidpattern with a higher concentration of braid strands or a different sizeof braid strands on the surface facing the neck of the aneurysm comparedto the surface radially opposite to it. In one embodiment, the surfacefacing the aneurysm is almost impermeable and the diametrically opposedsurface is highly permeable. Such a construction would direct blood flowaway from the aneurysm, but maintain blood flow to the side branches ofthe main vessel in which the occluding device is deployed.

In another embodiment, the occluding device has an asymmetrical braidcount along the longitudinal axis of the occluding device. This providesthe occluding device with a natural tendency to curve, and hence conformto the curved blood vessel. This reduces the stress exerted by theoccluding device on the vessel wall and thereby minimizing the chancesof aneurysm rupture. Additionally, because the occluding device isnaturally curved, this eliminates the need for the tip of themicro-catheter to be curved. Now, when the curved occluding device isloaded on to the tip of the micro-catheter, the tip takes the curvedshape of the occluding device. The occluding device could be pre-mountedinside the micro-catheter and can be delivered using a plunger, whichwill push the occluding device out of the micro-catheter when desired.The occluding device could be placed inside the micro-catheter in acompressed state. Upon exiting the micro-catheter, it could expand tothe size of the available lumen and maintain patency of the lumen andallow blood flow through the lumen. The occluding device could have alattice structure and the size of the openings in the lattice could varyalong the length of the occluding device. The size of the latticeopenings can be controlled by the braid count used to construct thelattice.

According to aspects of the invention, the occluding device can be usedto remodel an aneurysm within the vessel by, for example, neckreconstruction or balloon remodeling. The occluding device can be usedto form a barrier that retains occlusion material such as a well knowncoil or viscous fluids, such as “ONYX” by Microtherapeutics, within theaneurysm so that introduced material will not escape from within theaneurysm due to the lattice density of the occluding device in the areaof the aneurysm.

In another aspect of this invention, a device for occluding an aneurysmis disclosed. The device is a tubular with a plurality of perforationsdistributed on the wall of the member. The device is placed at the baseof the aneurysm covering the neck of the aneurysm such that the normalflow to the body of the aneurysm is disrupted and thereby generatingthrombus and ultimately occlusion of the aneurysm.

In yet another aspect of this invention, the device is a braided tubularmember. The braided strands are ribbons with rectangular cross section,wires with a circular cross section or polymeric strands.

In another embodiment, a device with a braided structure is made inorder to conform to a curved vessel in the body, where the density ofthe braid provides enough rigidity and radial strength. Additionally,the device can be compressed using a force less than 10 grams. Thisenables the device to be compliant with the artery as the arterial wallis pulsating. Also, the device is capable of bending upon applying aforce of less than 5 gram/cm.

Other aspects of the invention include methods corresponding to thedevices and systems described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention has other advantages and features which will be morereadily apparent from the following detailed description of theinvention and the appended claims, when taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is an illustration of an aneurysm, branch vessels and blood flowto the aneurysm.

FIGS. 2A and 2B illustrate one embodiment of an occluding device totreat aneurysms.

FIG. 3 is an illustration of the embodiment shown in FIG. 2 in acompressed state inside a micro-catheter.

FIG. 4A is another embodiment of an occluding device for treatinganeurysms.

FIGS. 4B and 4C illustrate cross sections of portions of ribbons thatcan be used to form the occluding device of FIG. 4A.

FIG. 5 shows the occluding device in a compressed state inside amicrocatheter being advanced out of the micro-catheter using a plunger.

FIG. 6 shows the compressed occluding device shown in FIG. 5 deployedoutside the micro-catheter and is in an expanded state.

FIG. 7 shows the deployed occluding device inside the lumen of a vesselspanning the neck of the aneurysm, a bifurcation and branch vessels.

FIG. 8 is a schematic showing the occluding device located in the lumenof a vessel and the change in the direction of the blood flow.

FIG. 9 shows the effect of a bending force on a conventional stentcompared to the occluding device of the present invention.

FIG. 10 demonstrates the flexibility of the current invention, comparedto a traditional stent, by the extent of the deformation for an appliedforce.

FIG. 11 shows the non-uniform density of the braid that provides thedesired curved occluding device.

FIG. 12 illustrates the difference in lattice density or porosity due tothe nonuniform density of the braiding of the occluding device.

FIG. 13 shows the varying lattice density occluding device covering theneck of an aneurysm.

FIGS. 14 and 15 show an embodiment of the vascular occluding devicewhere the lattice density is asymmetrical about the longitudinal axisnear the aneurysm neck.

FIG. 16 illustrates a bifurcated occluding device according to anembodiment of the present invention in which two occluding devices oflesser densities are combined to form a single bifurcated device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The devices shown in the accompanying drawings are intended for treatinganeurysms. They are generally deployed, using micro-catheters, at thelocation of a cerebral aneurysm that is intended to be treated. One suchsystem is disclosed in copending U.S. Patent Application titled “Systemand Method for Delivering and Deploying an Occluding Device Within aVessel”, U.S. application Ser. No. 11/136,398, filed on May 25, 2005,which is incorporated herein by reference in its entirety. Theembodiments of the endovascular occluding device according to aspects ofthe present invention is useful for treating cerebral aneurysms that arecommonly treated using surgical clips, microcoils or other embolicdevices.

FIG. 1 illustrates a typical cerebral aneurysm 10 in the brain. A neck11 of the aneurysm 10 can typically define an opening of between about 2to 25 mm. As is understood, the neck 11 connects the vessel 13 to thelumen 12 of the aneurysm 10. As can be seen in FIG. 1 , the blood flow 1within the vessel 13 is channeled through the lumen 12 and into theaneurysm. In response to the constant blood flow into the aneurysm, thewall 14 of lumen 12 continues to distend and presents a significant riskof rupturing. When the blood within the aneurysm 10 causes pressureagainst the wall 14 that exceeds the wall strength, the aneurysmruptures. The present invention could prevent such ruptures. Also shownin FIG. 1 are the bifurcation 15 and the side branches 16.

FIG. 2 illustrates one embodiment of an vascular occluding device 20 inaccordance with an aspect of the present invention. In the illustratedembodiment, the occluding device 20 has a substantially tubularstructure 22 defined by an outer surface 21, an inner surface 24 and athin wall that extends between the surfaces 21, 24. A plurality ofopenings 23 extend between the surfaces 21, 24 and allow for fluid flowfrom the interior of the occluding device 20 to the wall of the vessel.Occluding device 20 is radially compressible and longitudinallyadjustable.

FIG. 3 shows a micro-catheter 25 and the occluding device 20 inside themicrocatheter 25 in a compressed state prior to being released withinthe vasculature of the patient.

FIG. 4 illustrates another embodiment of the occluding device 30 havingtwo or more strands of material(s) 31, 32 wound in a helical fashion.The braiding of such material in this fashion results in a latticestructure 33. As can be understood, the dimension of the lattice 33 andthe formed interstices 34 is determined, at least in part, by thethickness of the strand materials, the number of strands and the numberof helices per unit length of the occluding device 30.

The occluding device 30 is radially compressible and radially expandablewithout the need for supplemental radially expanding force, such as aninflatable balloon. The occluding device 30 is constructed by windingthe two strands (31, 32 in opposite directions. In an embodiment, thestrands 31, 32 are in the shape of rectangular ribbon (See FIG. 4C). Theribbons can be formed of known flexible materials including shape memorymaterials, such as Nitinol, platinum and stainless steel.

The ribbon used as the braiding material for the strands 31, 32 caninclude a rectangular cross section 35 (FIG. 4C). As shown in FIGS. 4Cand 7 , the surface 36 that engages an inner surface of the vessel has alonger dimension (width) when compared to the wall 38 that extendsbetween the surfaces 36, 37 (thickness). A ribbon with rectangular crosssection has a higher recovery (expansive) force for the same wallthickness when compared to a wire with a circular (round) cross section.Additionally, a flat ribbon allows for more compact compression of theoccluding device 20 and causes less trauma to the vascular wall whendeployed because it distributes the radial expansion forces over agreater surface area. Similarly, flat ribbons form a more flexibledevice for a given lattice density because their surface area (width) isgreater for a given thickness in comparison to round wire devices.

While the illustrated embodiment discloses a ribbon having a rectangularcross section in which the length is greater than its thickness, theribbon for an alternative embodiment of the disclosed occluding devicesmay include a square cross section. In another alternative embodiment, afirst portion of the ribbon may include a first form of rectangularcross section and a second portion 39 of the ribbon (FIG. 4B) mayinclude a round, elliptical, oval or alternative form of rectangularcross section. For example, end sections of the ribbons may havesubstantially circular or oval cross section and the middle section ofthe ribbons could have a rectangular cross section.

In an alternative embodiment, the occluding device 30 can be formed bywinding more than two strands of ribbon. In an embodiment, the occludingdevice 30 could include as many as sixteen strands of ribbon. By usingstandard techniques employed in making radially expanding stents, onecan create an occluding device 30 with interstices 34 that are largerthan the thickness of the ribbon or diameter of the wire. The ribbonscan have different widths. In such an embodiment, the differentribbon(s) can have different width(s) to provide structure support tothe occluding device 30 and the vessel wall. The ribbons according tothe disclosed embodiments can also be formed of different materials. Forexample, one or more of the ribbons can be formed of a biocompatiblemetal material, such as those disclosed herein, and one or more of theribbons can be formed of a biocompatible polymer.

FIG. 5 shows the intravascular occluding device 30 in a radiallycompressed state located inside the micro-catheter 25. In oneembodiment, the occluding device 30 could be physically attached to thecatheter tip. This could be accomplished by constraining the occludingdevice 30 in the distal segment of the micro-catheter. Themicro-catheter 25 is slowly advanced over a guidewire (not shown) by aplunger 50 and when the tip of the micro-catheter 25 reaches theaneurysm, the occluding device is released from the tip. The occludingdevice 30 expands to the size of the vessel and the surface of theoccluding device 30 is now apposed to the vessel wall 15 as shown inFIG. 6 . Instruments and methods for delivering and deploying theoccluding device 30 are disclosed in the above-referenced copendingapplication.

With reference to FIG. 7 , the occluding device 30 is deployed insidethe lumen of a cerebral vessel 13 with an aneurysm 10. During itsdeployment, the proximal end 43 of the occluding device 30 is securelypositioned against the lumen wall of the vessel 13 before thebifurcation 15 and the distal end 45 of the occluding device 30 issecurely positioned against the lumen wall of the vessel 13 beyond theneck 11 of aneurysm 10. After the occluding device 30 is properlypositioned at the desired location within the vessel 13 (for example,see FIG. 7 ), flow inside the lumen of aneurysm 10 is significantlyminimized while the axial flow within the vessel 13 is not significantlycompromised, in part due to the minimal thickness of the walls 38.

The flow into the aneurysm 10 will be controlled by the lattice densityof the ribbons and the resulting surface coverage. Areas having greaterlattice densities will have reduced radial (lateral) flow. Conversely,areas of lesser lattice densities will allow significant radial flowthrough the occluding device 30. As discussed below, the occludingdevice 30 can have longitudinally extending (lateral) areas of differentdensities. In each of these areas, their circumferential densities canbe constant or vary. This provides different levels of flow throughadjacent lateral areas. The location within a vessel of the areas withgreater densities can be identified radiographically so that therelative position of the occluding device 30 to the aneurysm 10 and anyvascular branches 15, 16 can be determined. The occluding device 30 canalso include radiopaque markers.

The reduction of blood flow within the aneurysm 10 results in areduction in force against the wall 14 and a corresponding reduction inthe risk of vascular rupturing. When the force and volume of bloodentering the aneurysm 10 is reduced by the occluding device, the laminarflow into the aneurysm 10 is stopped and the blood within the aneurysmbegins to stagnate. Stagnation of blood, as opposed to continuous flowthrough the lumen 12 of the aneurysm 10, results in thrombosis in theaneurysm 10. This also protects the aneurysm from rupturing.Additionally, due to the density of the portion of the occluding device30 at the bifurcation 15, the openings (interstices) 34 in the occludingdevice 30 allow blood flow to continue to the bifurcation 15 and theside branches 16 of the vessel. If the bifurcation 15 is downstream ofthe aneurysm, as shown in FIG. 8 , the presence of the occluding device30 still channels the blood away from the aneurysm 10 and into thebifurcation 15.

The occluding devices described herein have the flexibility necessary toconform to the curvature of the vasculature. This is in contrast tocoronary stents that cause the vasculature to conform essentially totheir shape. The ability to conform to the shape of the vasculature ismore significant for neurovascular occluding devices than coronarystents, as the vasculature in the brain is smaller and more tortuous.Tables 1 and 2 demonstrate these characteristics of the claimedneurovascular occluding device. To demonstrate that the disclosedoccluding devices exhibit very desirable bending characteristics, thefollowing experiment was performed. The occluding device made by theinventors was set on a support surface 90 as shown in FIG. 9 . About 0.5inches of the occluding device 30 was left unsupported. Then, a measuredamount of force was applied to the unsupported tip until the occludingdevice was deflected by 90 degrees from the starting point. A similarlength of a commercially available coronary stent was subjected to thesame bending moment. The results are shown in Table 1. Similar to thereduced compressive force, the occluding device of the present inventionrequired an order of magnitude lower bending moment (0.005 lb-incompared to 0.05 lb-in for a coronary stent).

TABLE 1 Bending Force Required to Bend a 0.5″ Cantilever Made by theOcclusion Device Coronary stent commercially available stent 0.05 lb-inNeurovascular Occluding Device (30) 0.005 lb-in

The occluding devices according to the present invention also providesenhanced compressibility (i.e., for a given force how much compressioncould be achieved or to achieve a desired compression how much forceshould be exerted) compared to coronary stents. An intravascular devicethat is not highly compressible is going to exert more force on thevessel wall compared to a highly compressible device. This is ofsignificant clinical impact in the cerebral vasculature as it isdetrimental to have an intravascular device that has lowcompressibility.

TABLE 2 Compressive Force Required to Compress the Occluding device to50% of the Original Diameter (see FIG. 10) Coronary stent (commerciallyavailable 0.2 lb Neurovascular Occluding Device (30) 0.02 lb

FIGS. 11-13 show an embodiment of the occluding device 60 in which thelattice structure 63 of the occluding device 60 is non-uniform acrossthe length of the occluding device 60. In the mid-section 65 of theoccluding device 60, which is the section likely to be deployed at theneck of the aneurysm, the lattice density 63 a is intentionallyincreased to a value significantly higher than the lattice densityelsewhere in the occluding device 60. For example, as seen in FIG. 11 ,lattice density 63A is significantly higher than the lattice density 63in adjacent section 64. At one extreme, the lattice density (porosityprovided by the interstices) could be zero, i.e., the occluding device60 is completely impermeable. In another embodiment, the lattice density63A in mid-section 65 could be about 50%, while the lattice density inthe other sections 64 of the occluding device is about 25%. FIG. 12shows such the occluding device 60 in a curved configuration and FIG. 13shows this occluding device 60 deployed in the lumen of a vessel. FIG.13 also illustrates the part of the occluding device 60 with increasedlattice density 63A positioned along the neck of aneurysm 10. As withany of the disclosed occluding devices, the lattice density of at leastone portion of occluding device 60 can be between about 20% and about80%. The lattice density of these embodiments could be between about 25%and about 50%.

Another embodiment of the occluding device 300 is shown in FIGS. 14 and15 . In this embodiment, the occluding device 300 is deployed in lumenof a vessel with an aneurysm. The occluding device 300 includes asurface 310 that faces the lumen of the aneurysm. This surface 310 has asignificantly higher lattice density (smaller and/or fewer interstices)compared to the diametrically opposite surface 320. Due to the higherlattice density of surface 310, less blood flows into the lumen of theaneurysm. However, there is no negative impact on the blood flow to theside branches as the lattice density of the surface 320 facing the sidebranches is not reduced.

Any of the occluding devices disclosed herein can be used with a secondoccluding device to create a bifurcated occluding device 400 as shown inFIG. 16 . This device could be created in vivo. In forming the occludingdevice 400, a portion of a first occluding device 410 having a lowdensity can be combined with a portion of a second occluding device 410that also has a low density. The occluding devices 410, 420 can be anyof those discussed herein. After these portions of the two occludingdevices 410, 420 are combined in an interwoven fashion to form aninterwoven region 425, the remaining portions 414, 424 can branch off indifferent directions, thereby extending along two braches of thebifurcation. Areas outside of the interwoven region 425 can have greaterlattice density for treating an aneurysm or lesser lattice density forallowing flow to branches 15, 16 of the vessel.

The density of the lattice for each of the disclosed occluding devicescan be about 20% to about 80% of the surface area of its occludingdevice. In an embodiment, the lattice density can be about 20% to about50% of the surface area of its occluding device. In yet anotherembodiment, the lattice density can be about 20% to about 305 of thesurface area of its occluding device.

A typical occluding device having sixteen strand braids with 0.005 inchwide ribbon, 30 picks per inch (PPI) (number of crosses/points ofcontact per inch), and 0.09 inch outer diameter has approximately 30% oflattice density (surface covered by the ribbon). In the embodimentsdisclosed herein, the ribbon can be about 0.001 inch thick with a widthof between about 0.002 inch to about 0.005 inch. In an embodiment, theribbon has a thickness of about 0.004 inch. For a 16-strands ribbon thatis about 0.001 inch thick and about 0.004 inch wide, the coverage for 50PPI, 40 PPI, and 30 PPI will have 40%, 32% and 24% approximate surfacecoverage, respectively. For a 16-strands ribbon that is about 0.001 inchthick and about 0.005 inch wide, the coverage for 50 PPI, 40 PPI, and 30PPI will be about 50%, 40% and 30% approximate surface coverage,respectively.

In choosing a size for the ribbon, one must consider that, when theribbons are bundled up, will they traverse through a micro-catheter. Forexample, sixteen strands of a 0.006 inch wide ribbon may not passthrough a micro-catheter having an internal diameter of 0.027 inch orless. However, as the width of ribbons become smaller, the recoverystrength may decrease proportionally.

While other strand geometry may be used, these other geometries, such asround, will limit the device due to their thickness dimension. Forexample, a round wire with a 0.002 inch diameter will occupy up to 0.008inch in cross sectional space within the vessel. This space can impactand disrupt the blood flow through the vessel. The flow in the vesselcan be disrupted with this change in diameter.

Although the detailed description contains many specifics, these shouldnot be construed as limiting the scope of the invention but merely asillustrating different examples and aspects of the invention. It shouldbe appreciated that the scope of the invention includes otherembodiments not discussed in detail above. Various other modifications,changes and variations which will be apparent to those skilled in theart may be made in the arrangement, operation and details of the methodand apparatus of the present invention disclosed herein withoutdeparting from the spirit and scope of the invention as defined in theappended claims. Therefore, the scope of the invention should bedetermined by the appended claims and their legal equivalents.Furthermore, no element, component or method step is intended to bededicated to the public regardless of whether the element, component ormethod step is explicitly recited in the claims.

In the claims, reference to an element in the singular is not intendedto mean “one and only one” unless explicitly stated, but rather is meantto mean “one or more.” In addition, it is not necessary for a device ormethod to address every problem that is solvable by differentembodiments of the invention in order to be encompassed by the claims.

The invention claimed is:
 1. A device for positioning within a bloodvessel for treatment of an aneurysm, the device comprising: a pluralityof braided members, wherein the braided members form a lattice structurealong the length of the device, each of the braided members comprisingan inner surface and an outer surface, the outer surface beingconfigured for positioning adjacent an inner wall of a vessel, and theouter surface forming a portion of an outer circumference of the devicebetween first and second ends of the device, the plurality of braidedmembers forming a plurality of openings extending between adjacentmembers of the device, the outer surfaces of the plurality of braidedmembers comprising between about 20 percent to about 50 percent of atotal circumferential area of the device, wherein the device isconfigured to freely bend without permanent deformation 90 degrees abouta fulcrum upon application of a bending moment of 0.005 lb-in to thedevice, and to be compressed to 50% of an original diameter of thedevice upon application of a force of less than 10 grams, when thedevice is fully deployed from a delivery catheter, and wherein at leastsome of the braided members comprise platinum.
 2. The device of claim 1,wherein the openings occupy between about 50 to about 80 percent of thetotal circumferential area of the device.
 3. The device of claim 1,comprising a length that can be adjusted during deployment such that thedeployed length of the occluding device can be adjusted after theoccluding device is loaded within a delivery catheter.
 4. The device ofclaim 1, comprising regions for positioning proximate a branch or feederportion of the vessel, the regions having a lesser lattice densityrelative to a region intended to be positioned proximate an aneurysm. 5.The device of claim 1, wherein at least two of the braided members havedifferent cross-sectional dimensions.
 6. The device of claim 1, whereinthe device is configured to have a surface coverage between 20% to 50%.7. The device of claim 1, wherein the braided members are round in crosssection.
 8. A braided device for occluding a portion of a vesselcomprising: an elongated flexible structure having an asymmetricalbraided pattern of braided members, the members having an inner surfaceand an outer surface, the outer surface being configured for positioningadjacent an inner wall of a vessel, the outer surface forming a portionof an outer circumference of the device between first and second ends ofthe device, the outer surfaces of the plurality of braided memberscomprising between about 20 percent to about 50 percent of a totalcircumferential area of the device; wherein the members form a latticestructure along the length of the device, wherein the device, uponapplication of a bending moment of 0.005 lb-in, is configured to bendwithout permanent deformation 90 degrees about a longitudinal axis ofthe device, and wherein the device is configured to freely bend about afulcrum and to be compressed to 50% of an original diameter of thedevice upon application of a force of less than 10 grams when the deviceis fully deployed within a vessel, and wherein the device is configuredto have a surface coverage between 20% to 50%.
 9. The device of claim 8,wherein a first portion of the braided pattern allows a first amount ofradial blood flow to pass there through and a second portion of thebraided pattern allows a second amount of radial blood flow therethrough, the first amount being greater than the second amount; whereinthe first and second portions include different lattice densities. 10.The device of claim 8, comprising a length that can be adjusted duringdeployment such that a deployed length of the occluding device can beadjusted after the occluding device is loaded within a deliverycatheter.
 11. The device of claim 8, wherein at least two of the braidedmembers have different cross-sectional dimensions.
 12. The device ofclaim 8, wherein at least some of the braided members comprise platinum.13. The device of claim 8, wherein the braided members are round incross section.
 14. A braided occlusion device, for occluding an aneurysmin a vessel, the device comprising: an elongate structure having abraided pattern of more than two braided members, the braided membershaving an inner surface and an outer surface, the outer surface beingconfigured for positioning adjacent an inner wall of a vessel, the outersurface forming a portion of an outer circumference of the devicebetween first and second ends of the device, the outer surfaces of theplurality of braided members comprising between about 20 percent toabout 50 percent of a total circumferential area of the device, whereinthe braided members form a lattice structure along the length of thedevice, the elongate structure having a compressed configuration, forintravascular delivery of the structure to a target site, with acompressed cross-sectional measurement, and an expanded configurationwith an expanded cross-sectional measurement greater than the compressedcross-sectional measurement; wherein the elongate structure isconfigured to change from the compressed configuration to the expandedconfiguration when unrestrained, and wherein, when in the expandedconfiguration, a first portion of the elongate structure deflectswithout permanent deformation 90 degrees about a fulcrum and relative toa second portion of the elongate structure when a bending moment of0.005 lb-in is applied to the first portion, and the elongate structureis configured to be compressed to 50% of an original diameter of thedevice upon application of a force of less than 10 grams, and wherein atleast some of the braided members comprise platinum.
 15. The device ofclaim 14, wherein at least two of the braided members have differentcross-sectional dimensions.
 16. The device of claim 14, wherein thedevice is configured to have a surface coverage between 20% to 50%. 17.The device of claim 14, wherein the braided members are round in crosssection.